Model photochemical smog

Wayne, L., R. Danchick, M. Weisburd, A. Kokin, and A. Stein. Modeling photochemical smog on a computer for decision-making. J. Air Pollut. Control Assoc. 21 334-340, 1971. 

G. Z. Whitten and co-workers. Modeling of Simulated Photochemical Smog with Kinetic Mechanism, Vols. I and II, Report No. EPA-600/3-79-001a, U.S. Environmental Protection Agency, Research Triangle Park, N.C., 1979. 

Eschenroeder, A. Q., and Martinez, J. R., "Mathematical Modeling of Photochemical Smog," No. IMR- 1210. General Research Corp., Santa Barbara, CA, 1969. 

PBM (Photochemical Box Model) is a simple stationary single-cell model with a variable height lid designed to provide volume-integrated hour averages of ozone and otlier photochemical smog pollutants for an urban area for a single day of simulation. 

Atkinson, R. and Lloyd, A. C. (1984). Evaluation of kinetic and mechanistic data for modeling of photochemical smog. /. Phps. Chem. Ref. Data 13,315-444. 

Our concept of a volume source (see Figure 2) is intentionally vague, because few good examples exist. However, photochemical smog is produced over a volume of air is this just part of a fate model or should it be considered a source ... 

Rational air pollution control strategies require the establishment of reliable relationships between air quality and emission (Chapter 5). Diffusion models for inert (nonreacting) agents have long been used in air pollution control and in the study of air pollution effects. Major advances have been made in incorporating the complex chemical reaction schemes of photochemical smog in diffusion models for air basins. In addition to these deterministic models, statistical relationships that are based on aerometric data and that relate oxidant concentrations to emission measurements have been determined. 

One must not take too seriously the results from complex simulations at this stage of our knowledge. In particular the development of sound reaction schemes and realistic smog models require [sic] much more quantitative kinetic information as to the detailed reaction paths which appear to be important in photochemical smog.... There is no question that as such information becomes available, present models will require substantial changes. 

Air quality simulation models for photochemical pollutants were reviewed by Johnson et al. for a new edition of Air Pollution. Some of the models developed for simulating photochemical smog were reviewed from the viewpoints of module logic and evaluation. The Los Angeles-based developments were outlined, including the format and preprocessing of emission inventory data and meteorologic data. Lumped-param-... 

Eschenroeder, A. Q., J. R. Martinez, and R. A. Nordsieck. Evaluation of a Diffusion Model for Photochemical Smog Simulation. EPA-R4-73-012a. Santa Barbara, Calif. General Research Corporation, 1972. 226 pp. 

Sklarew, R. C., A. J. Fabrick, and J. E. Prager. Mathematical modeling of photochemical smog using the FiCK method. J. Air Pollut. Control Assoc. 22 865-869, 1972. 

The development of models requires more knowledge about the chemical, physical, morphologic, and flow properties of the mucus layer the kinetics of the reactions of ozone in the mucus and tissue layers and the molecular diffusivity of ozone in these layers. Similar information is needed for the hydroperozy and singlet oxygen, O, (a A), free radicals, which are reactive interme ates in photochemical smog. 

Clearly, environmental chamber studies are very useful tools in examining the chemical relationships between emissions and air quality and for carrying out related (e.g., exposure) studies. Use of these chambers has permitted the systematic variation of individual parameters under controlled conditions, unlike ambient air studies, where the continuous injection of pollutants and the effects of meteorology are often difficult to assess and to quantitatively incorporate into the data analysis. Chamber studies have also provided the basis for the validation of computer kinetic models. Finally, they have provided important kinetic and mechanistic information on some of the individual reactions occurring during photochemical smog formation. 

The solvent should not contain substances that contribute significantly to the production of photochemical smog and troposphere ozone. The volatile organic content of the product, as used, should not exceed 50 g/L. None of the components of the product will have a maximum incremental reactivity (MIR) exceeding 1.9 g Ofg of compound (the MIR for toluene). MIR values can be obtained from the maximum incremental reactivity list found in Appendix VII of the California Air Resources Board s California Exhaust Emission Standards and Test Procedures for 1988 and Subsequent Model Passenger Cars, Light-Duty Trucks and Medium-Duty Vehicles as amended on September 22, 1993. 

A model is developed to account for the chemical features of photochemical smog observed in laboratory and atmospheric studies. A detailed mechanism consisting of some 60 reactions is proposed for a prototype smog system, the photooxidation in air of propylene in the presence of oxides of nitrogen at low concentrations. The rate equations for this detailed mechanism have been numerically integrated to calculate the time-concentration behavior of all the constituents of the system. The model has been used to examine the effects of varying relative and absolute concentrations of the reactants. The conclusions of this examination provide a framework for the analysis of the more complicated atmospheric problem. Some of the key questions related to the atmospheric chemistry have been discussed in terms of the detailed model. 

Tn recent years, a number of reaction models have been proposed to account for the chemical features of photochemical smog observed in atmospheric and laboratory studies (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11). Because of the complexity of smog chemistry and a lack of detailed knowledge of many relevant elementary reactions, numerous assumptions and simplifications are made in these mechanistic interpretations. A model for the chemistry of smog is presented here with a critical evaluation of the factors that control the major course of the reactions. The photooxidation of propylene (CsHq) in the presence of nitric oxide and nitrogen dioxide (NO + NO2 = NO, ) is used as a prototype for this study. 

Several types of models are commonly used to describe the dispersion of atmospheric contaminants. Among these are the box, plume, and puff models. None are suitable, however, for describing the coupled transport and reaction phenomena that characterize atmospheres in which chemical reaction processes are important. Simulation models that have been proposed for the prediction of concentrations of photochemically formed pollutants in an urban airshed are reviewed here. The development of a generalized kinetic mechanism for photochemical smog suitable for inclusion in an urban airshed model, the treatment of emissions from automobiles, aircraft, power plants, and distributed sources, and the treatment of temporal and spatial variations of primary meteorological parameters are also discussed. 

Before extensive application of these plume models, Frenkiel used a puff model to study photochemical smog in Los Angeles (5). A point source was assumed to be centered within each four-mile-square in the... 

Related Work on Photochemical Smog Modeling. Models for photochemical air pollution require extensions of earlier methods. Coupled chemical reactions and radiation attenuation in the ultraviolet introduce nonlinearities into the analysis. Consequently, the superposition of linear solutions from collections of point, line, or finite-area sources may inaccurately describe the chemical interactions with meteorological conditions in the air basin. Chemical evolution of pollutants, therefore, demands a step-by-step description to refiect the cumulative effects of the processes occurring. 

---